In recent years, many electronic devices have been specialized for personal use. For example, mobile phones are personalized for music choices, ring tones, and the like. Users of the personal electronic devices may also have personal information such as phone numbers, credit card numbers, addresses, and the like stored on the personal electronic devices.
To insure privacy and security of personal services and information, user authentication may be used. For example, usage may be restricted to an authorized user or a set of authorized users by using a password. In this manner, a specified function of an electronic apparatus cannot be used unless authentication by password is successfully performed. Existing security measures may block password inputs after a user makes a few incorrect inputs. However, an authorized user may input a few mistaken password entries before inputting the password correctly. As a result, the authorized user may be blocked from inputting passwords before being able to input the password correctly. This puts a burden on the authorized user. Therefore, there is a need for authentication technologies that minimize burdens on the authorized user and deter unauthorized users.